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# electricity

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1. a 100W light bulb is plugged into a standard 120V outlet. how much does it cost per month (31 days) to leave the light turned on? assume electricity costs 6 cents per kw.h What is the resistance of the bulb? what is the current in the bulb?
2. the watt is a unit of power, the hour is a unit of time.

power is a rate of doing work i.e. Energy/time

so multiply watts by hours and you get kWh which is a unit of energy (i.e. what you are being charged for when the electric company sends you an energy bill)

it's not an SI unit of energy but can be converted to one easily enough because 1Joule = 1 Watt second

how many seconds in 1 hour?
how many Watts in 1 kW?

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